FIGS. 12(a) and 12(b) show a slide assist device of the following Patent Document 1. Characteristics of the device are that a main body frame slidably disposes the sliding door or the door; a projecting body 9 which is an actuating member is provided in the sliding door or the door; and the sliding door or the door is drawn in through the projecting body 9 by a draw-in unit which is a main portion of the slide assist device provided in the main body frame. The draw-in unit comprises a case 1 attached to the main body frame; sliders 2A and 2B slidably placed on the case 1; latches 5 and 5 pivotally supported relative to each slider through a shaft 8; and an urging device 3. The projecting body 9 is provided to protrude on an upper end surface side of the sliding door or the door.
There, the case 1 is formed slenderly and also thinly because the case 1 is disposed along a guiding groove of the main body frame. Each slider 2A and 2B includes a convex portion 22 provided on upper and lower surfaces. Each convex portion 22 fits into guide grooves 12b and 16b provided on the upper and lower surfaces of the case 1, and each convex portion is slid while being guided by the upper and lower guide devices. Also, each latch 5 includes a protrusion 52 provided on the upper and lower surfaces. The respective protrusions 52 fit into guide grooves 14 and 19 provided on the upper and lower surfaces of the case 1, and the respective protrusions 52 slide while being guided by the upper and lower guide devices. The respective guide grooves 14 and 19 include straight grooves 14a and 19a parallel to the guide grooves 12b and 16b, and locking grooves 14b and 19b with an approximately L shape provided on both sides of the straight grooves 14a and 19a. 
In the above-mentioned slide assist device, the latches 5 on both sides in FIG. 12(a) and the latch 5 on the right side in FIG. 12(b) are in a standby position. In the latches 5, in the standby position, the upper and lower protrusions 52 are locked in the corresponding locking grooves 14b and 19b, and positions of the latches 5 are controlled against an urging force accumulated in the urging device 3 together with the slider 2A. Then, from a state shown in FIG. 12(a), when the sliding door or the door which is in an open position on the left side (not shown in the figure) is operated to slide in a closing direction from the open position, the projecting body 9 hits against an inner surface of a hook portion 50 of the corresponding latch 5 of the draw-in unit, and the latch 5 is rotated by the force thereof, and is switched to a draw-in position as shown on the left side of FIG. 12(b) from the standby position. In the draw-in position, in a state wherein the latch 5 has constrained the projecting body 9 inside the hook portion, the upper and lower protrusions 52 enter into the straight grooves 14a and 19a from the locking grooves 14b and 19b so as to release the locking. Consequently, the latch 5 and the slider 2A are slid by the urging force accumulated in the urging device 3, and automatically switch the sliding door or the door to a closed position through the projecting body 9. Also, from the closed position, by an opening operation of the sliding door or the door, when the projecting body 9 is slid to the left side of the figure together with the latch 5, accompanied by that, the urging force is accumulated in the urging device 3. Moreover, when the sliding door or the door is moved in an open direction, the latch 5 is switched to the standby position again.